548 Notices of Memoirs—Dr. Hicks—Cambrian in Wales. 
NOTICES OF MEMOTRS. 
Sheets 
ABSTRACTS OF PAPERS READ BEFORE THE British ASSOCIATION, 
NorringHam, SepremsBer, 1893. 
J.—On Tue Base oF THE CamBRIAN IN Wates. By H. Hicks, M.D., 
E.R.S., F.G.S. 
F there be, as has been maintained by the author and others, a 
very marked unconformity at the base of the rocks usually 
classed as Cambrian in Wales, the evidence furnished by an examina- 
tion of those basal beds which indicate shore conditions is of the 
utmost importance. The author, therefore, in this paper gives a 
summary of the results bearing on this question which he has 
obtained in his examinations of these rocks in Wales. 
PEMBROKESHIRE. 
St. Davids.—The basal beds are exposed on the north and south 
sides of the pre-Cambrian Axis. Where faults do not intervene the 
lowest beds are rough conglomerates from 60 to 150 feet in thick- 
ness, in which pebbles over a foot in diameter are very frequently 
met with. The matrix and pebbles vary constantly, as they rest on 
different parts of the pre-Cambrian Axis, and there is the clearest 
evidence of an unconformity between the conglomerates and the 
highest beds of the Pebidian in this area. The overlying beds, 
which are grits and sandstones, are ripple-marked and show other 
proofs of having been deposited in shallow shore-water. The author 
has recently re-examined the basal beds in this area, and has accumu- 
lated additional evidence in support of the above view. 
Ramsey Island.—The Cambrian conglomerates here rest on pre- 
Cambrian felstones and breccias. The pebbles are mainly well- 
rolled fragments of felstones cemented together by a felsitic matrix. 
Pebbles of quartzite and other materials are occasionally found, but 
the main amount of the material was undoubtedly derived from the 
rocks immediately underlying the conglomerates. The underlying 
rocks had undergone the marked changes now visible in them before 
the fragments in the conglomerates had been broken off. 
Trefgarn.—The pre-Cambrian rocks in this area are mainly felstones 
of a peculiar type and volcanic ash. The conglomerates which repose 
on these rocks contain pebbles of large size, which have been proved 
by microscopical examination to be identical in character with the 
rocks on whose eroded surface they repose. Here again the marked 
similarity in the minutest particulars between the rolled fragments 
and the underlying rocks proves indisputably that the peculiar 
changes which these rocks have undergone must have taken place 
before the fragments were broken off, therefore in pre-Cambrian times. 
MERIONETHSHIRE. 
Harlech Mountain.—Near the centre of the well-known anticlinal 
of Cambrian rocks in the Harlech Mountain conglomerates are 
exposed which contain fragments of granitoid rocks, felstones, etc., 
in addition to pebbles of quartzites and quartz, and it is clear that 
